An intelligent network (IN) can be regarded as a service-independent (telecommunications) network. That is, intelligence is taken out of switches and placed in one or more computer nodes that are distributed throughout the network. This provides the network operator with the means to develop and control services more efficiently. Moreover, new capabilities can be rapidly introduced into the network. Once introduced, services are easily customized to meet individual needs of a subscriber.
Specific IN standards are, for example, CAMEL (Customized Application for Mobile Network Enhanced Logic), INAP (Intelligent Network Application Protocol), WIN (Wireless Intelligent Network), CS1 (Capability set 1) and CS1+ (Capability set 1 extended). The CAMEL network feature is defined in the 3GPP TS (3rd Generation Partnership Project Technical Specification) 22.078 and enables the use of Operator Specific Services (OSS) by a subscriber, even when roaming outside the Home-PLMN (Public Land Mobile Network). The CAMEL feature is part of the call control in circuit switched (CS) networks; in addition its interworking with GPRS networks has been specified. The main functional components implementing the CAMEL functionalities are the gsmSCF (GSM Service Control Function) and gsmSSF (GSM Service Switching Function). These functional components interact with MSC (Mobile Services Switching Centre), HLR (Home Location Register) and VLR (Visiting Location Register) of CS networks as described in the 3GGP TS 23.078.
For transmitting multimedia calls over a CS domain, specific codecs are available, namely the synchronous transparent UDI/RDI (un/restricted digital information) codecs with 64 kbit/s and 56 kbit/s, respectively. Throughout this document, the term “multimedia” comprises in particular UDI/RDI multimedia.
The services in a CS domain generally include multimedia and speech (further, less popular services such as facsimile transmission exist). Service change and service fallback related to these services is defined in the 3GGP TS 23.172, “CS multimedia service UDI/RDI fallback and service modification”, commonly referred to as the “Service Change and UDI Fallback Feature” (SCUDIF).
Service change in this respect is defined as follows: when two services (multimedia and speech) are available during the active state of a call, users may request a service change to switch between the two services.
Service fallback is defined as follows: when two services (multimedia and speech) are proposed but only one of them is available or wanted, only the service available (preferred or less preferred) is selected, and the other one is discarded.
The SCUDIF feature is available to multimedia calls and permits successful call establishment even when end-to-end CS multimedia data transmission is not possible (fallback to speech) or when signalling of the feature is not possible in the network (fallback to preferred services or speech). Furthermore, the feature allows for a swap between a multimedia service and basic speech during an already established call. The general requirements for SCUDIF are defined in TS 23.172, section 4.1.
The interaction of SCUDIF and CAMEL does, however, not provide any mechanism to autonomously decide on network-initiated service change or service fallback, i.e. scenarios in which it would be appropriate from a network point of view to select, change or set a bearer for the offered service by the network during call establishment or the active phase of a call. In addition, the network cannot control a userinitiated service change request. Examples for such scenarios include user profile or charging restrictions, e.g., insufficient credit for a subscriber to initiate a multimedia call or maintain an already established call.
Whereas any such feature of network-controlled service change and/or service fallback might be implemented e.g. by an MNO (Mobile Network Operator) as an OSS in the network under the control of the operator, the user will be subject to a different behaviour when roaming outside the H-PLMN (Home PLMN), i.e. in a V-PLMN (Visited PLMN). Although the CAMEL feature provides mechanisms to support OSS of the MNO not covered by standardised services when roaming outside the H-PLMN, the interactions of CAMEL with SCUDIF are limited to notifications of the gsmSCF of, for example, the selected services during user-initiated service change after the service change procedure has been successfully completed.
It is an object of the invention to propose a technique for permitting a network-initiated service change or service fallback during call setup or for an established connection in CAMEL-enabled networks.